The interview book is a waste of time, you can glean more from PPrune and it will be more recent than from that book. Updating at less than 6 monthly intervals would not jeopardise your application.
If you think that the recruitment department judge a persons application based on how often they update, you are sadly mistaken. Yes it shows you are keen but unless it provides some additional information that changes your circumstances, it will be of little value. So an hours update every 6 months or so does seem reasonable but if you have changed jets, seats etc it would be good to provide that info immediately.
Cerberus